How I evaluate and treat thrombocytopenia in the intensive care unit patient

Understanding, assessing and treating immune, endothelial and haemostasis dysfunctions in bacterial sepsis

The interplay between the immune system, coagulation, and endothelium is critical in regulating the host response to infection. However, in sepsis and other critical illnesses, a dysregulated immune response can lead to excessive alterations in these mechanisms, resulting in coagulopathy, endothelial dysfunction, and multi-organ dysfunction. This review aims to provide a comprehensive analysis of the pathophysiological mechanisms that govern the complex interplay between immune dysfunction, endothelial dysfunction, and coagulation in sepsis. It emphasises clinical significance, evaluation methods, and potential therapeutic interventions. Understanding these mechanisms is essential for developing effective treatments that can modulate the immune response, mitigate thrombosis, restore endothelial function, and ultimately improve patient survival.

Prophylactic versus restrictive platelet transfusion strategy in patients with haematological malignancies in the ICU setting, a propensity-score analysis

PURPOSE

Prophylactic platelet transfusions (PT) aim to reduce bleeding. We assessed whether restrictive PT compared to prophylactic strategy could apply in ICU.

MATERIAL AND METHODS

We conducted a retrospective monocentric study including patients >18 yo with haematological malignancy admitted to the ICU with thrombocytopenia <20 G/L between 2018 and 2021. Patients were classified in 2 groups according transfusion strategy applied during the first 3 days: prophylactic or restrictive transfusion.

RESULTS

180 patients were included, 87 and 93 in the restrictive and prophylactic groups respectively. After propensity-score analysis, 2 groups of 54 matched patients were analyzed. Restrictive strategy led to a significant reduction in PT with incidence rate for 100-ICU-patients-days of 34.9 and 49.9, incidence rate ratio = 0.699 [0.5-0.9], p = 0.006, representing a 31% decrease. Decreased PT persisted until day 28 with platelet concentrates transfusions-free days at day 28 of 21 [13-25] and 16.5 [10.2-21] in the 2 groups (p = 0.04). Restrictive strategy did not result in higher grade ≥ 2 bleeding. Transfusion efficiency was low with similar number of days with platelet <10 or < 20 G/L regardless of strategy. Platelet transfusion strategy was not associated with 28-day mortality. Platelet nadir <5G/L was associated with day-28 mortality with HR = 1.882 [1.011-3.055], p = 0.046.

CONCLUSION

A restrictive PT strategy appears feasible in the ICU.

Loss of plasma fibrinogen contributes to platelet hyporeactivity in rats with septic shock

INTRODUCTION

Dysregulated host response to infection causes life-threatening organ dysfunction. Excessive inflammation and abnormal blood coagulation can lead to disseminated intravascular coagulation (DIC) and multiple-organ failure in the late sepsis stages. Platelet function impairment in sepsis contributes to bleeding, secondary infection, and tissue injury. Platelet transfusion is considered in patients with sepsis with DIC and bleeding; however, its benefits are limited and of low quality. Fibrinogen plays a crucial role in platelet function, and establishing a fibrin network binds to activated integrin αIIbβ3 and promotes outside-in signaling that amplifies platelet functions. However, the role of fibrinogen in sepsis-induced platelet dysfunction remains unclear.

MATERIALS AND METHODS

We evaluated the effects of fibrinogen on platelet hyporeactivity during septic shock in adult male Wistar rats using lipopolysaccharide (LPS) injection and cecal ligation and puncture (CLP) surgery. Changes in the hemodynamic, biochemical, and coagulation parameters were examined. Platelet activation and aggregation were measured using whole-blood assay, 96-well plate-based aggregometry, and light-transmission aggregometry. Additionally, platelet adhesion, spreading, and fibrin clot retraction were evaluated.

RESULTS

Rats with LPS- and CLP-induced sepsis displayed considerable decreases in plasma fibrinogen levels and platelet aggregation, adhesion, spreading, and clot retraction. The aggregation of platelets obtained from rats with sepsis was markedly augmented by fibrinogen supplementation. Additionally, fibrinogen administration improved platelet adhesion, spreading, and clot retraction in rats with sepsis.

CONCLUSIONS

Fibrinogen supplementation could serve as a potential therapeutic intervention for alleviating platelet hyporeactivity in patients with sepsis and bleeding.

Effect of ferric citrate hydrate on fibroblast growth factor 23 and platelets in non-dialysis-dependent chronic kidney disease and non-chronic kidney disease patients with iron deficiency anemia

BACKGROUND

Iron deficiency anemia (IDA) increases levels of C-terminal fibroblast growth factor 23 (cFGF23) and platelet count (PLT), each of which is associated with cardiovascular events. Therefore, we hypothesized that iron replacement with ferric citrate hydrate (FC) would decrease cFGF23 levels and PLT in patients with IDA.

METHODS

In a randomized, open-label, multicenter, 24-week clinical trial, patients with non-dialysis-dependent chronic kidney disease (CKD) and non-CKD complicated by IDA (8.0 ≤ hemoglobin < 11.0 g/dL; and serum ferritin < 50 ng/mL [CKD]; < 12 ng/mL [non-CKD]) were randomized 1:1 to FC-low (500 mg: approximately 120 mg elemental iron/day) or FC-high (1000 mg: approximately 240 mg elemental iron/day). If sufficient iron replacement had been achieved after week 8, further treatment was discontinued.

RESULTS

Seventy-three patients were allocated to FC-low (CKD n = 21, non-CKD n = 15) and FC-high (CKD n = 21, non-CKD n = 16). Regardless of CKD status, FC increased serum ferritin and transferrin saturation, did not change intact FGF23 or serum phosphorus, but decreased cFGF23. In FC-low group, median changes in cFGF23 from baseline to week 8 were -58.00 RU/mL in CKD and -725.00 RU/mL in non-CKD; in FC-high group, the median changes were -66.00 RU/mL in CKD and -649.50 RU/mL in non-CKD. By week 8, FC treatment normalized PLT in all patients with high PLT at baseline (>35.2 × 104/µL; FC-low: 1 CKD, 8 non-CKD; FC-high: 3 CKD, 8 non-CKD).

CONCLUSION

Regardless of CKD status, iron replacement with FC decreased elevated cFGF23 levels and normalized elevated PLT in patients with IDA.

CLINICAL TRIAL REGISTRATION NUMBER

jRCT2080223943.

Severe thrombocytopenia associated to bevacizumab in a patient with scleroderma, gastrointestinal angiodysplasias and refractory gastrointestinal bleeding

This case report discusses the medical history of a 64-year-old woman diagnosed with scleroderma and diffuse gastrointestinal angiodysplasia. The patient received bevacizumab (BVZ) therapy to address gastrointestinal bleeding that was unresponsive to endoscopic treatment. Subsequently, she developed severe thrombocytopenia. Although there were suspicions of an immune-mediated mechanism resulting from BVZ treatment, the laboratory results did not provide conclusive evidence. The patient underwent transfusions, received gamma globulin, and was treated with Romiplostim. Over time, her platelet levels gradually improved, and the bleeding was successfully controlled. It's worth noting that BVZ-induced thrombocytopenia is a relatively rare yet severe adverse effect. Recognizing and understanding the mechanisms behind thrombocytopenia is essential for developing safer treatment approaches. Further research is required to identify potential risk factors associated with this condition.

Reduced IgG2 with thrombocytopenia predicts mortality in patients with influenza pneumonia

BACKGROUND

Thrombocytopenia is a common disorder during influenza that is related to high mortality.

OBJECTIVES

A prospective study was performed to investigate the association of immunoglobulin subclass changes accompanying incident thrombocytopenia with clinical outcomes in patients with severe influenza.

METHODS

96 influenza patients were recruited and divided into two groups, patients with thrombocytopenia (n = 30) and patients without thrombocytopenia (n = 66). Plasma microarrays were used for quantitative analysis of immunoglobulins. The endpoint was 28-day mortality. Continuous platelet count, d-dimer, level of each Ig subclass and other variables were compared between the two groups. Kaplan-Meier curve was taken to analyze the 28-day survival rate of the two groups and Cox regression analysis was performed to identify variables independently associated with 28-day mortality.

RESULTS

Patients with thrombocytopenia had significantly high values of d-dimer at admission and when platelet lowest with high SOFA score. Their IgA2, IgG2, and IgG4 values were also lower than those without thrombocytopenia. Patients without thrombocytopenia had a higher 28-day survival rate than those in the thrombocytopenia group. In the multivariate Cox regression model, age (HR = 1.036, 95%CI = 1.011-1.062), IgG2 (HR = 0.990, 95%CI = 0.982-0.998), platelet minimum within 28 days (HR = 0.991, 95%CI = 0.982-0.999) and d-dimer when platelet lowest (HR = 1.091, 95%CI = 1.047-1.137) were independently related to 28-day mortality.

CONCLUSION

Decreased IgG2 may be associated with thrombocytopenia. A coexistence of thrombocytopenia, IgG2 reduction and d-dimer elevation may improve the accuracy of mortality prediction in patients with influenza pneumonia.

How I diagnose and treat thrombocytopenia in geriatric patients

ABSTRACT

Thrombocytopenia in older individuals is a common but diagnostically challenging condition that has variable clinical impact to those who are affected. Diagnostic approach requires evaluation of the preexisting clinical conditions, detailed review of medications, and assessment for disorders that warrant urgent treatment. In this article, we describe a systematic approach to diagnosis of thrombocytopenia and present a schematic review for management strategies. Three clinical scenarios are presented that are relevant for their prevalence and management challenges in an older adult population. The first scenario addresses primary immune thrombocytopenia (ITP) and reviews different treatment options. The second one addresses complications of thrombocytopenia in management of the myelodysplastic syndrome. The last one reviews diagnostic challenges of drug-induced ITP.

Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study (PLOT-ICU)

PURPOSE

Thrombocytopenia (platelet count < 150 × 109/L) is common in intensive care unit (ICU) patients and is likely associated with worse outcomes. In this study we present international contemporary data on thrombocytopenia in ICU patients.

METHODS

We conducted a prospective cohort study in adult ICU patients in 52 ICUs across 10 countries. We assessed frequencies of thrombocytopenia, use of platelet transfusions and clinical outcomes including mortality. We evaluated pre-selected potential risk factors for the development of thrombocytopenia during ICU stay and associations between thrombocytopenia at ICU admission and 90-day mortality using pre-specified logistic regression analyses.

RESULTS

We analysed 1166 ICU patients; the median age was 63 years and 39.5% were female. Overall, 43.2% (95% confidence interval (CI) 40.4-46.1) had thrombocytopenia; 23.4% (20-26) had thrombocytopenia at ICU admission, and 19.8% (17.6-22.2) developed thrombocytopenia during their ICU stay. Absence of acquired immune deficiency syndrome (AIDS), non-cancer-related immune deficiency, liver failure, male sex, septic shock, and bleeding at ICU admission were associated with the development of thrombocytopenia during ICU stay. Among patients with thrombocytopenia, 22.6% received platelet transfusion(s), and 64.3% of in-ICU transfusions were prophylactic. Patients with thrombocytopenia had higher occurrences of bleeding and death, fewer days alive without the use of life-support, and fewer days alive and out of hospital. Thrombocytopenia at ICU admission was associated with 90-day mortality (adjusted odds ratio 1.7; 95% CI 1.19-2.42).

CONCLUSION

Thrombocytopenia occurred in 43% of critically ill patients and was associated with worse outcomes including increased mortality. Platelet transfusions were given to 23% of patients with thrombocytopenia and most were prophylactic.

The interaction of thrombocytopenia, hemorrhage, and platelet transfusion in venoarterial extracorporeal membrane oxygenation: a multicenter observational study

BACKGROUND

Thrombocytopenia, hemorrhage and platelet transfusion are common in patients supported with venoarterial extracorporeal membrane oxygenation (VA ECMO). However, current literature is limited to small single-center experiences with high degrees of heterogeneity. Therefore, we aimed to ascertain in a multicenter study the course and occurrence rate of thrombocytopenia, and to assess the association between thrombocytopenia, hemorrhage and platelet transfusion during VA ECMO.

METHODS

This was a sub-study of a multicenter (N = 16) study on transfusion practices in patients on VA ECMO, in which a retrospective cohort (Jan-2018-Jul-2019) focusing on platelets was selected. The primary outcome was thrombocytopenia during VA ECMO, defined as mild (100-150·109/L), moderate (50-100·109/L) and severe (< 50·109/L). Secondary outcomes included the occurrence rate of platelet transfusion, and the association between thrombocytopenia, hemorrhage and platelet transfusion, assessed through mixed-effect models.

RESULTS

Of the 419 patients included, median platelet count at admission was 179·109/L. During VA ECMO, almost all (N = 398, 95%) patients developed a thrombocytopenia, of which a significant part severe (N = 179, 45%). One or more platelet transfusions were administered in 226 patients (54%), whereas 207 patients (49%) suffered a hemorrhagic event during VA ECMO. In non-bleeding patients, still one in three patients received a platelet transfusion. The strongest association to receive a platelet transfusion was found in the presence of severe thrombocytopenia (adjusted OR 31.8, 95% CI 17.9-56.5). After including an interaction term of hemorrhage and thrombocytopenia, this even increased up to an OR of 110 (95% CI 34-360).

CONCLUSIONS

Thrombocytopenia has a higher occurrence than is currently recognized. Severe thrombocytopenia is strongly associated with platelet transfusion. Future studies should focus on the etiology of severe thrombocytopenia during ECMO, as well as identifying indications and platelet thresholds for transfusion in the absence of bleeding.

TRIAL REGISTRATION

This study was registered at the Netherlands Trial Registry at February 26th, 2020 with number NL8413 and can currently be found at https://trialsearch.who.int/Trial2.aspx?TrialID=NL8413.

Can we lower the platelet threshold of ≥ 50 × 109/L for performing a lumbar puncture safely in patients with hematological malignancies?

Lumbar punctures (LP) are routinely used to administer intrathecal chemotherapy for children and adults with hematologic malignancies. The current guidelines suggest a platelet threshold of ≥ 50 × 10⁹/L prior to LP for intrathecal chemotherapy (ITC). This can be challenging in patients with hematological malignancies who are thrombocytopenic. We conducted a retrospective chart review of 900 LPs for ITC and compared adverse events in patients with a platelet count of ≥ 50 × 10⁹/L and < 50 × 10⁹/L. Cohort 1 included 682 LPs (75.8%) with a pre-procedure platelet count ≥ 50 × 10⁹/L, and cohort 2 included 218 LPs (24.2%) with a pre-procedure platelet count < 50 × 10⁹/L. Cohort 2 was further subdivided into pre-procedure platelet counts of 41 × 10⁹/L-49 × 10⁹/L (n = 43), 31 × 10⁹/L-40 × 10⁹/L (n = 77), 21 × 10⁹/L-30 × 10⁹/L (n = 84), and 11 × 10⁹/L-20 × 10⁹/L (n = 14). Among 900 LP procedures, a pre-procedure platelet count < 50 × 10⁹/L did not demonstrate a higher rate of post-procedure adverse events (6.5% vs 6.8%, p = 0.8237). When cohort 2 was further stratified, the cohort with a pre-procedure platelet count of 21 × 10⁹/L-30 × 10⁹/L had the highest percentage of complications from LP (9.5%) and the highest rates of traumatic taps with observed LP RBC count > 200 (35.7%, p = 0.0015). The rate of red blood cells (RBC) in the CSF was significantly higher in the group with platelets < 50 × 10⁹/L with observed LP RBC count ≥ 200 (31.2% vs 20.5%, p = 0.0016), ≥ 500 (27.1% vs 14.6%, p < 0.0001), and ≥ 1000 (23% vs 11.6%, p < 0.0001). No instances of epidural hematomas were seen. We found no significant difference in bleeding complications between patients undergoing LPs for ITC with a platelet count above or below 50 × 10⁹/L.

Association between PT, PT-INR, and in-hospital mortality in critically ill patients with tumors: A retrospective cohort study

Objectives

Prothrombin time (PT) and PT-INR are independent predictors of mortality in patients with cancer. The PT and PT-INR of cancer patients are independent predictive variables of mortality. However, whether the PT or PT-INR is related to in-hospital mortality in severely ill patients with tumors remains unknown.

Design

This was a case-control study based on a multicenter public database.

Settings

This study is a secondary analysis of data extracted from 2014 to 2015 from the Electronic Intensive Care Unit Collaborative Research Database.

Participants

The data relevant to seriously ill patients with tumors were obtained from 208 hospitals spread throughout the USA. This research included a total of 200,859 participants. After the samples were screened for patients with combination malignancies and prolonged PT-INR or PT, the remaining 1745 and 1764 participants, respectively, were included in the final data analysis.

Primary and secondary outcome measures

The key evaluation methodology was the PT count and PT-INR, and the main outcome was the in-hospital mortality rate.

Results

After controlling for confounding variables, we found a curvilinear connection between PT-INR and in-hospital mortality (p < 0.001), and the inflection point was 2.5. When PT-INR was less than 2.5, an increase in PT-INR was positively associated with in-hospital mortality (OR 1.62, 95% CI 1.24 to 2.13), whereas when PT-INR was greater than 2.5, in-hospital mortality was relatively stable and higher than the baseline before the inflection point. Similarly, our study indicated that the PT exhibited a curvilinear connection with in-hospital mortality. On the left side of the inflection point (PT <22), a rise in the PT was positively linked with in-hospital mortality (OR 1.08, 95% CI 1.04 to 1.13, p < 0.001). On the right side of the inflection point, the baseline PT was above 22, and the in-hospital mortality was stable and higher than the PT count in the prior range (OR 1.01, 95% CI 0.97 to 1.04, 0.7056).

Conclusion

Our findings revealed that there is a curved rather than a linear link between the PT or PT-INR and in-hospital mortality in critically ill cancer patients. When these two laboratory results are below the inflection point, comprehensive therapy should be employed to reduce the count; when these two laboratory results are above the inflection point, every effort should be made to reduce the numerical value to a value below the inflection point.

RISK OF HOSPITAL MORTALITY IN CRITICALLY ILL PATIENTS WITH TRANSIENT AND PERSISTENT THROMBOCYTOPENIA: A RETROSPECTIVE STUDY

ABSTRACT

Background: Thrombocytopenia (TP), a common occurrence among patients admitted to the intensive care unit (ICU), is significantly associated with prolonged ventilator use, prolonged ICU stay, and increased mortality. The duration of TP serves as an indicator of patient outcome, although the exact duration of TP associated with poor patient outcome remains unclear. In this study, the data of 3,291 patients on their first admission to the ICU between January 2010 and December 2020 were retrospectively analyzed. Participants were divided into the no TP, TP 1-2 days, TP 3-6 days, and TP ≥7 days groups based on the duration of TP. External validation was performed using the Medical Information Mart for Intensive Care III data set. Results: A longer duration of TP was significantly associated with high volume of transfusion and high hospital mortality ( P < 0.01), and 37.3% of the participants developed TP during their ICU stay. The results of Kaplan-Meier survival analysis and Cox regression analysis after excluding the effects of patients who died shortly after ICU admission revealed the absence of significant differences between the no TP and TP 1-2 days groups ( P > 0.05). However, when the duration of TP exceeded 2 days, patient mortality increased with an increase in the duration of TP ( P < 0.01). Similar findings were obtained with the Medical Information Mart for Intensive Care III data set. Conclusions: The duration of TP in critically ill patients is positively correlated with poor patient outcome. We classified TP as either transient TP or persistent TP based on a cutoff duration of 2 days. Monitoring the duration of TP may aid in the prediction of patients' outcome in the ICU.

How I use platelet transfusions

Platelet transfusions are commonly administered for the prevention or treatment of bleeding in patients with acquired thrombocytopenia across a range of clinical contexts. Recent data, including randomized trials, have highlighted uncertainties in the risk-benefit balance of this therapy, which is the subject of this review. Hemovigilance systems report that platelets are the most frequently implicated component in transfusion reactions. There is considerable variation in platelet count increment after platelet transfusion, and limited evidence of efficacy for clinical outcomes, including prevention of bleeding. Bleeding events commonly occur despite the different policies for platelet transfusion prophylaxis. The underlying mechanisms of harm reported in randomized trials may be related to the role of platelets beyond hemostasis, including mediating inflammation. Research supports the implementation of a restrictive platelet transfusion policy. Research is needed to better understand the impact of platelet donation characteristics on outcomes, and to determine the optimal thresholds for platelet transfusion before invasive procedures or major surgery (eg, laparotomy). Platelet transfusion policies should move toward a risk-adapted approach that does not focus solely on platelet count.

Inflammatory platelet death drives sepsis

Thrombocytopenia is common in severe sepsis and is associated with an increased risk of mortality. A new study shows that platelet pyroptosis initiated during infection promotes a feedforward loop of neutrophil-mediated inflammation that worsens outcomes during sepsis.

Severe thrombocytopenia in adults undergoing extracorporeal membrane oxygenation is predictive of thrombosis

Extracorporeal membrane oxygenation (ECMO) provides lifesaving circulatory support and gas exchange, although hematologic complications are frequent. The relationship between ECMO and severe thrombocytopenia (platelet count <50 × 109/L) remains ill-defined. We performed a cohort study of 67 patients who received ECMO between 2016 and 2019, of which 65.7% received veno-arterial (VA) ECMO and 34.3% received veno-venous (VV) ECMO. All patients received heparin and 25.4% received antiplatelet therapy. In total, 23.9% of patients had a thrombotic event and 67.2% had a hemorrhagic event. 38.8% of patients developed severe thrombocytopenia. Severe thrombocytopenia was more common in patients with lower baseline platelet counts and increased the likelihood of thrombosis by 365% (OR 3.65, 95% CI 1.13-11.8, P = .031), while the type of ECMO (VA or VV) was not predictive of severe thrombocytopenia (P = .764). Multivariate logistic regression controlling for additional clinical variables found that severe thrombocytopenia predicted thrombosis (OR 3.65, CI 1.13-11.78, P = .031). Over a quarter of patients requiring ECMO developed severe thrombocytopenia in our cohort, which was associated with an increased risk of thrombosis and in-hospital mortality. Additional prospective observation is required to clarify the clinical implications of severe thrombocytopenia in the ECMO patient population.

Association between platelets and in-hospital mortality in critically ill patients with tumours: a retrospective cohort study

OBJECTIVES

Platelet count is an independent predictor of mortality in patients with cancer. It remains unknown whether the platelet count is related to in-hospital mortality in severely ill patients with tumours.

DESIGN

A retrospective study based on a dataset from a multicentre cohort.

SETTING

This was a secondary analysis of data from one Electronic Intensive Care Unit Collaborative Research Database survey cycle (2014-2015).

PARTICIPANTS

The data pertaining to severely ill patients with tumours were collected from 208 hospitals located across the USA. This study initially a total of 200 859 participants. After the population was limited to patients with combined tumours and platelet deficiencies, the remaining 2628 people were included in the final data analysis.

PRIMARY AND SECONDARY OUTCOME MEASURES

The main measure was the platelet count, and the main outcome was in-hospital mortality.

RESULTS

After adjustment for the covariates, the platelet count had a curvilinear relationship with in-hospital mortality (p<0.001). The first inflection point was 18.4 (per 10 change). On the left side of the first inflection point (platelet count ≤184 'x10ˆ9/L), an increase of 10 in the platelet count was negatively associated with in-hospital mortality (OR 0.92, 95% CI 0.89 to 0.95, p<0.001). The second inflection point was 44.5 (per 10 change). Additional increases of 10 in the platelet count thereafter were positively associated with hospital mortality (OR 1.13, 95% CI 1.00 to 1.28, p=0.0454). The baseline platelet count was in the range of 184 'x10ˆ9/L-445 'x10ˆ9/L(p=0.0525), and the hospital mortality was lower than the baseline platelet count in other ranges.

CONCLUSIONS

The relationship between platelet count and in-hospital mortality in critically ill patients with tumours was curvilinear. The lowest in-hospital mortality was associated with platelet count between 184 'x10ˆ9/Land 445 'x10ˆ9/L. This indicates that both high and low platelet count should receive attention in clinical practice.

Evolution of Platelet Activation Parameters During Septic Shock in Intensive Care Unit

During severe sepsis, platelet activation may induce disseminate microvascular thrombosis, which play a key role in critical organ failure. Crucially, most of the studies in this field have explored platelet-leukocyte interactions in animal models, or explored platelets under the spectrum of thrombocytopenia or disseminated intravascular coagulation and have not taken into account the complex interplay that might exist between platelets and leukocytes during human septic shock nor the kinetics of platelet activation. Here, we assessed platelet activation parameters at the admission of patients with sepsis to the intensive care unit (ICU) and 48 hours later. Twenty-two patients were enrolled in the study, thirteen (59.1%) of whom were thrombocytopenic. The control group was composed of twelve infection-free patients admitted during the study period. The activation parameters studied included platelet-leukocyte interactions, assessed by flow cytometry in whole blood, as well as membrane surface and soluble platelet activation markers measured by flow cytometry and dedicated ELISA kits. We also investigated platelet aggregation and secretion responses of patients with sepsis following stimulation, compared to controls. At admission, the level of circulating monocyte-platelet and neutrophil-platelet heterotypic aggregates was significantly higher in sepsis patients compared to controls and returned to a level comparable to controls or even below 48 hours later. Basal levels of CD62P and CD63 platelet membrane exposure at admission and 48 hours later were low and similar to controls. In contrast, plasma level of soluble GPVI and soluble CD40 ligand was significantly increased in septic patients, at the two times of analysis, reflecting previous platelet activation. Platelet aggregation and secretion responses induced by specific agonists were significantly decreased in septic conditions, particularly 48 hours after admission. Hence, we have observed for the first time that critically ill septic patients compared to controls have both an early and durable platelet activation while their circulating platelets are less responsive to different agonists.

Heparin-induced Thrombocytopenia: Perioperative Diagnosis and Management

Heparin-induced thrombocytopenia is a severe prothrombotic disease. Timely diagnosis and treatment are essential. Application of diagnostic algorithms based on validated clinical scoring tools and rapid, specific laboratory assays may improve outcomes.

Pulmonary coagulation and fibrinolysis abnormalities that favor fibrin deposition in the lungs of mouse antibody-mediated transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a life-threatening disease caused by blood transfusion. However, its pathogenesis is poorly understood and specific therapies are not available. Experimental and clinical studies have indicated that alveolar fibrin deposition serves a pathological role in acute lung injuries. The present study investigated whether pulmonary fibrin deposition occurs in a TRALI mouse model and the possible mechanisms underlying this deposition. The TRALI model was established by priming male Balb/c mice with lipopolysaccharide (LPS) 18 h prior to injection of an anti-major histocompatibility complex class I (MHC-I) antibody. Untreated mice and mice administered LPS plus isotype antibody served as controls. At 2 h after TRALI induction, blood and lung tissue were collected. Disease characteristics were assessed based on lung tissue histology, inflammatory responses and alterations in the alveolar-capillary barrier. Immunofluorescence staining was used to detect pulmonary fibrin deposition, platelets and fibrin-platelet interactions. Levels of plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex (TATc), tissue factor pathway inhibitor (TFPI), coagulation factor activity and fibrin degradation product (FDP) in lung tissue homogenates were measured. Severe lung injury, increased inflammatory responses and a damaged alveolar-capillary barrier in the LPS-primed, anti-MHC-I antibody-administered mice indicated that the TRALI model was successfully established. Fibrin deposition, fibrin-platelet interactions and platelets accumulation in the lungs of mouse models were clearly promoted. Additionally, levels of TATc, coagulation factor V (FV), TFPI and PAI-1 were elevated, whereas FDP level was decreased in TRALI mice. In conclusion, both impaired fibrinolysis and enhanced coagulation, which might be induced by boosted FV activity, increased pulmonary platelets accumulation and enhanced fibrin-platelet interactions and contributed to pulmonary fibrin deposition in TRALI mice. The results provided a therapeutic rationale to target abnormalities in either coagulation or fibrinolysis pathways for antibody-mediated TRALI.

Functional Status After Pulmonary Rehabilitation as a Predictor of Weaning Success and Survival in Patients Requiring Prolonged Mechanical Ventilation

Background: Comprehensive rehabilitation programs are recommended for patients with prolonged mechanical ventilation (PMV) to facilitate functional recovery and ventilator weaning, but whether the functional status after rehabilitation influences outcome has not been clearly evaluated. This study aimed to investigate the association between post-rehabilitation functional status and weaning and survival outcome in PMV patients. Methods: We retrospectively enrolled PMV patients admitted to the respiratory care center (RCC), a post-ICU weaning facility with protocolized rehabilitation program, from January 2016 through December 2017. Functional status was measured by the de Morton Mobility Index (DEMMI), with a cut-off value set at 20 points. The primary outcomes were the weaning status at RCC discharge and hospital survival. The secondary outcomes were overall survival and survival at 3 months after RCC discharge. We followed patients until 3 months after RCC discharge or death. Logistic and Cox regressions were performed to identify significant parameters associated with weaning success and survival. Results: In total, 320 patients were enrolled. The weaning success rate was 71.6%. The survival rate at RCC discharge, hospital discharge, and 3 months after RCC discharge was 89.1, 77.5, and 66.6%, respectively. Post-rehabilitation DEMMI ≥ 20 (odds ratio [OR], 3.514; 95% confidence interval [CI], 1.436-8.598; P = 0.006) was the most significantly associated with weaning success. The weaning success and higher post-rehabilitation DEMMI were the two most significant independent factors associated with both hospital survival (weaning success, OR, 12.272; 95% CI, 5.281-28.517; P < 0.001; post-rehabilitation DEMMI ≥ 20, OR, 6.298; 95% CI, 1.302-30.477; P = 0.022) and survival at 3 months after RCC discharge (weaning success, OR, 38.788; 95% CI, 11.505-130.762; P < 0.001; post-rehabilitation DEMMI ≥ 20, OR, 4.830; 95% CI, 1.072-21.756; P = 0.040). Post-rehabilitation DEMMI ≥ 20 remained significantly association with overall survival at 3 months after RCC discharge (hazard ratio, 0.237; 95% CI, 0.072-0.785; P = 0.018). Conclusions: Post-rehabilitation functional status of PMV patients was independently associated with weaning success, as well as hospital and 3-month overall survival after RCC discharge. Post-rehabilitation, but not pre-rehabilitation, functional status was a significant parameter associated with weaning success and survival in patients requiring PMV.

Pseudothrombocytopenia-A Review on Causes, Occurrence and Clinical Implications

Pseudothrombocytopenia (PTCP), a relative common finding in clinical laboratories, can lead to diagnostic errors, overtreatment, and further (even invasive) unnecessary testing. Clinical consequences with potential life-threatening events (e.g., unnecessary platelet transfusion, inappropriate treatment including splenectomy or corticosteroids) are still observed when PTCP is not readily detected. The phenomenon is even more complex when occurring with different anticoagulants. In this review we present a case of multi-anticoagulant PTCP, where we studied different parameters including temperature, amikacin supplementation, measurement methods, and type of anticoagulant. Prevalence, clinical risk factors, pre-analytical and analytical factors, along with clinical implications, will be discussed. The detection of an anticoagulant-dependent PTCP does not necessarily imply the presence of specific disorders. Conversely, the incidence of PTCP seems higher in patients receiving low molecular weight heparin, during hospitalization, or in men aged 50 years or older. New analytical technologies, such as fluorescence or optical platelet counting, will be soon overturning traditional algorithms and represent valuable diagnostic aids. A practical laboratory approach, based on current knowledge of PTCP, is finally proposed for overcoming spuriously low platelet counts.

A modern multidisciplinary approach to the treatment of enterocutaneous fistulas in Crohn's disease patients

INTRODUCTION

Enterocutaneous fistulas (ECFs) is a manifestation of penetrating Crohn's disease (CD) that is challenging to treat and has considerable morbidity and mortality rates.

AREAS COVERED

This review aims to explore the practical and updated principles for the optimal treatment of ECFs in CD patients.

EXPERT OPINION

Optimal ECF management requires a multidisciplinary approach. Treatment first includes fluid resuscitation and electrolyte rebalancing with control of sepsis by means of antibiotics and, when indicated, drainage of infected collections. Subsequent therapeutic steps include nutritional support, control of the fistula output and treatment of peristomal skin. Anti-TNF-α therapy seems to have limited utility only after sepsis is resolved and intestinal stenosis excluded. However, ECFs heal in only approximately one-third of cases without surgical intervention. Thus, correct surgical timing combined with adequate nutritional support, sepsis resolution and skin care is considered the appropriate preoperative setting.

Innate immune receptors in platelets and platelet-leukocyte interactions

Platelets are chief cells in hemostasis. Apart from their hemostatic roles, platelets are major inflammatory effector cells that can influence both innate and adaptive immune responses. Activated platelets have thromboinflammatory functions linking hemostatic and immune responses in several physiological and pathological conditions. Among many ways in which platelets exert these functions, platelet expression of pattern recognition receptors (PRRs), including TLR, Nod-like receptor, and C-type lectin receptor families, plays major roles in sensing and responding to pathogen-associated or damage-associated molecular patterns (PAMPs and DAMPs, respectively). In this review, an increasing body of evidence is compiled showing the participation of platelet innate immune receptors, including PRRs, in infectious diseases, sterile inflammation, and cancer. How platelet recognition of endogenous DAMPs participates in sterile inflammatory diseases and thrombosis is discussed. In addition, platelet recognition of both PAMPs and DAMPs initiates platelet-mediated inflammation and vascular thrombosis in infectious diseases, including viral, bacterial, and parasite infections. The study also focuses on the involvement of innate immune receptors in platelet activation during cancer, and their contribution to tumor microenvironment development and metastasis. Finally, how innate immune receptors participate in platelet communication with leukocytes, modulating leukocyte-mediated inflammation and immune functions, is highlighted. These cell communication processes, including platelet-induced release of neutrophil extracellular traps, platelet Ag presentation to T-cells and platelet modulation of monocyte cytokine secretion are discussed in the context of infectious and sterile diseases of major concern in human health, including cardiovascular diseases, dengue, HIV infection, sepsis, and cancer.

Platelet Count within the Normal Range at Hospital Admission is Associated with Mortality in Patients with Community-Acquired Pneumonia

Background

Apart from their hemostatic role, platelets are immune cells that play a role in fighting infections. The presence of thrombocytopenia and thrombocytosis at hospital admission are predictors of mortality in community-acquired pneumonia patients. We hypothesized that variations in platelet counts within the normal range also may be associated with mortality in these patients.

Methods

The study included all adults in the North and Central Denmark Regions with a first acute hospital admission for community-acquired pneumonia during 2006-2012. We assessed the association between the first platelet count within ± 24 hours of admission (within the normal range of 150 to 400 x 10⁹/L) and 30-day mortality using Cox models. Analyses were adjusted for age, sex, Charlson Comorbidity Index score, hemoglobin level, leukocyte count, and creatinine level at admission.

Results

Among the 12,905 study patients, 30-day mortality was 12.4%. The mean platelet count upon admission was 250 × 10⁹/L. Compared with the 250-275 × 10⁹/L category, platelet counts of 151-175 were associated with a lower 30-day mortality (adjusted hazard ratio [aHR]: 0.79, 95% confidence interval [CI]: 0.63-0.99), while higher platelet counts were associated with a higher 30-day mortality (351-375 × 10⁹/L, aHR: 1.34, 95% CI: 1.07-1.68; 376-400× 10⁹/L, aHR: 1.21, 95% CI: 0.94-1.56).

Conclusion

Platelet counts, even within the normal range, are associated with mortality in adult patients hospitalized for community-acquired pneumonia.

Types and outcomes of cytopenia in critically ill patients

Cytopenia is common complication in critically ill patients. Aim: Incidence and pattern of different types of cytopenia as well as its impact on mortality and length of stay in critically ill patients were evaluated. Methods: Critically ill patients with any kind of cytopenia for more than 2 days were evaluated. Results: Anemia was the most common type of cytopenia in the patients (99.14%), followed by lymphocytopenia (32.17%), thrombocytopenia (27.82%), and leukopenia (19.13%). Mortality rate was significantly higher in patients with anemia (p < 0.0001), thrombocytopenia (p < 0.0001), leukopenia (p < 0.0001), neutropenia (p = 0.004), lymphopenia (p = 0.002) and pancytopenia (p < 0.0001). Higher duration of anemia, lymphopenia and thrombocytopenia were associated with longer intensive care unit stay (p < 0.0001, p < 0.0001 and p < 0.001, respectively). Conclusion: Among all assessed variables, incidence of thrombocytopenia could independently predict the mortality.

Thrombocytopenia and platelet course on hospital mortality in neurological intensive care unit: a retrospective observational study from large database

BACKGROUND

Thrombocytopenia (TP) has been shown to be an independent predictor of mortality in the intensive care unit (ICU) patients. Studies are lacking in the neurological ICU (NICU) population. The aim was to evaluate the incidence of TP in NICU and the relationship between TP and outcomes.

METHODS

We conducted a retrospective multicenter study of prospectively collected data of all patients admitted to the NICU between 2014 and 2015 from a large database (eICU Collaborative Research Database). The main exposure was TP at admission and TP developed during NICU stay. Multivariable logistic regression and Cox proportional hazard models were used to evaluate the relationship of TP at admission and platelet course with hospital mortality. The primary outcome was hospital mortality.

RESULTS

7450 patients in NICU from 17 hospitals were included. Hospital mortality was 9%. TP at admission was present in 20% of patients, TP developed during NICU stay was present in 13.2% of patients. TP at admission was not associated with hospital mortality after adjusting for confounders (OR 1.14 [95% CI 0.92-1.41, p = 0.237]). Hospital mortality of continuous TP during NICU stay was 15% while hospital mortality of recovery from TP at admission was 6% (p < 0.001). Patients with TP developed during NICU stay had higher odds ratio for hospital mortality (OR 1.65 [95% CI 1.3-2.09, p < 0.001]).

CONCLUSIONS

Thrombocytopenia is common in NICU and patients who have thrombocytopenia not resolving have increased mortality. Patients' recovery from thrombocytopenia may predict a good prognosis.

Detection of Platelet-Activating Antibodies Associated with Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a prothrombotic immune drug reaction caused by platelet-activating antibodies that in most instances recognize platelet factor 4 (PF4)/polyanion complexes. Platelet activation assays (i.e., functional assays) are more specific than immunoassays, since they are able to discern clinically relevant heparin-induced antibodies. All functional assays used for HIT diagnosis share the same principle, as they assess the ability of serum/plasma from suspected HIT patients to activate fresh platelets from healthy donors in the presence of several concentrations of heparin. Depending on the assay, donors’ platelets are stimulated either in whole blood (WB), platelet-rich plasma (PRP), or in a buffer medium (washed platelets, WP). In addition, the activation endpoint studied varies from one assay to another: platelet aggregation, membrane expression of markers of platelet activation, release of platelet granules. Tests with WP are more sensitive and serotonin release assay (SRA) is considered to be the current gold standard, but functional assays suffer from certain limitations regarding their sensitivity, specificity, complexity, and/or accessibility. However, the strict adherence to adequate preanalytical conditions, the use of selected platelet donors and the inclusion of positive and negative controls in each run are key points that ensure their performances.

Heparin-induced thrombocytopenia: Diagnostic challenges in intensive care patients especially with extracorporeal circulation

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious drug induced reaction that may be associated with life threatening complications. Platelet-activating antibodies directed against platelet factor 4 (PF4)/heparin complexes cause the disease. The diagnosis of HIT is challenging, as thrombocytopenia is a frequent finding in intensive care (ICU) patient population, especially during extracorporeal membrane oxygenation.

OBJECTIVE

To investigate the performance of a diagnostic algorithm for HIT in ICU patients.

METHODS

ICU patients who developed thrombocytopenia or thrombosis under heparin treatment were included in this study. The pretest probability for HIT was estimated using the 4Ts-score and patient's sera were tested using two rapid immunoassays (RA) LFI-HIT and PaGIA (from Milenia Biotec and DiaMed), and within 72 h using the IgG enzyme immunoassay (EIA) from Hyphen and the heparin induced platelet activation assay (HIPA).

RESULTS

392 consecutive ICU patients with suspected HIT were enrolled in this study, of whom 83/392 (21.2%) patients had extracorporeal circulation. Sera from 120/392 (30.6%) and 98/392 (25.0%) patients revealed positive results in RA and IgG EIA, respectively. The HIPA test revealed heparin-dependent platelet activation in a total of 15/392 (3.8%) ICU patients (3 medical and 12 surgical patients). In addition, sera from 7 patients revealed indeterminate HIPA results, of whom 2 patients had a clinical course compatible with HIT.

CONCLUSIONS

Data from our study confirm the high frequency of IgG PF4/heparin antibodies in ICU patients under unfractionated heparin and shows that the combination of 4Ts-score and RA does not reduce the laboratory overinvestigation for HIT in these patients.

Thrombocytopenia in the Intensive Care Unit

The evaluation and management of thrombocytopenia is a daily challenge for clinicians in the intensive care unit (ICU). Thrombocytopenia is incredibly common, present in upwards of 60% of ICU patients. Additionally, thrombocytopenia in the critically ill is rarely caused by a single etiology. Several causes of thrombocytopenia in the ICU including heparin-induced thrombocytopenia (HIT) and thrombotic thrombocytopenic purpura demand urgent recognition and intervention. This chapter provides a general overview of thrombocytopenia in the ICU and highlights important diagnostic and management considerations for some of the most common etiologies.

Pneumococcal Bacteremia Complicated by Hemophagocytic Lymphohistiocytosis

From pneumonia to pericarditis, from sepsis to splenic abscess, Streptococcus pneumoniae is the causative agent of a diverse array of pyogenic disease. With the introduction of vaccines and effective antibiotic treatments, the incidence of complicated streptococcal infection has declined. We report a case of S. pneumoniae bacteremia, in the setting of occult sinusitis, complicated by hemophagocytic lymphohistiocytosis (HLH), disseminated intravascular coagulation (DIC), and recurrent pneumococcal infection. Although severe streptococcal infection has been associated with immunodeficiency or splenectomy, no such predisposition was identified in our patient. We discuss the association of streptococcal infection with HLH and DIC and review occult sinusitis as a source of pneumococcal bacteremia, with the goal of enhancing the "illness scripts" of general medical practitioners to include such entities.

Hemizygosity for the gene encoding glycoprotein Ibβ is not responsible for macrothrombocytopenia and bleeding in patients with 22q11 deletion syndrome

Essentials How thrombocytopenia relates to bleeding in 22q11 deletion syndrome (22q11DS) is not clear. Bleeding severity, platelet count and volume, and GPIBB were examined in patients with 22q11DS. Macrothrombocytopenia and bleeding typified imperfectly overlapping subsets of 22q11DS patients. GPIBB hemizygosity does not cause macrothrombocytopenia or bleeding in patients with 22q11DS. SUMMARY: Background and objectives Macrothrombocytopenia and bleeding are frequently associated with 22q11 deletion syndrome (22q11DS). GPIBB, which encodes the glycoprotein (GP) Ibβ subunit of GPIb-IX-V, is commonly deleted in patients with 22q11DS. Absence of functional GPIb-IX-V causes Bernard-Soulier syndrome, which is a severe bleeding disorder characterized by macrothrombocytopenia. Patients with 22q11DS are often obligate hemizygotes for GPIBB, and those with only a pathogenically disrupted copy of GPIBB present with Bernard-Soulier syndrome. The objective of this study was to determine how GPIBB hemizygosity and sequence variation relate to macrothrombocytopenia and bleeding in patients with 22q11DS who do not have Bernard-Soulier syndrome. Patients/methods We thoroughly characterized bleeding severity, mean platelet volume, platelet count and GPIBB copy number and sequence in patients with 22q11DS. Results and conclusions Macrothrombocytopenia and mild bleeding were observed in incompletely overlapping subsets of patients, and GPIBB copy number and sequence variation did not correlate with either macrothrombocytopenia or bleeding in patients with 22q11DS. These findings indicate that GPIBB hemizygosity does not result in either macrothrombocytopenia or bleeding in these patients. Alternative genetic causes of macrothrombocytopenia, potential causes of acquired thrombocytopenia and bleeding and ways in which platelet size, platelet count and GPIBB sequence information can be used to aid in the diagnosis and management of patients with 22q11DS are discussed.

Limited impact of clinician education on reducing inappropriate PF4 testing for heparin-induced thrombocytopenia

A high frequency of PF4-ELISA testing in patients suspected to have heparin-induced thrombocytopenia (HIT) despite low 4T scores has been observed in multiple medical centers. Education of clinicians has been suggested to reduce inappropriate testing. We determined trends of PF4-ELISA testing in our institution after the introduction of a HIT education program for clinicians. A HIT Program was developed that included ongoing education, individual feedback, and continuous clinical audit of PF4-ELISA utilization. To assess the impact of education on PF4-ELISA testing trends, we conducted a prospective cohort review of all adult patients who had a PF4-ELISA ordered over a 3 month period (the last quarter of the academic year). 72 PF4-ELISA tests were ordered during the study period. Prospectively calculated 4T scores by investigators revealed 60 low-risk (83.3%), 9 intermediate-risk (12.5%), and 3 high-risk (4.16%). We observed divergent 4T scores with the ordering clinician calculating a higher 4T score compared to the Hematology Quality Improvement (QI) team. The majority of PF4-ELISA testing was ordered by the intensive care units (ICUs) (n = 32, 44.44%). Our study revealed that the frequency of calculation of 4T scores remains poor with the majority inappropriately performed in the ICU setting, with ordering clinicians calculating higher 4T scores than the Hematology QI team. This suggests that clinician education alone is insufficient. Introducing mandatory 4T score calculation prior to PF4-ELISA testing may not be helpful as ordering clinicians can bypass the restriction through inaccurate 4T score calculation.

Thrombocytopenia in Intensive Care Unit

How to cite this article: Aluru N, Samavedam S. Thrombocytopenia in Intensive Care Unit. Indian J Crit Care Med 2019;23(Suppl 3):S185–S188.

Bacterial contamination of platelets for transfusion: strategies for prevention

Platelet transfusions carry greater risks of infection, sepsis, and death than any other blood product, owing primarily to bacterial contamination. Many patients may be at particular risk, including critically ill patients in the intensive care unit. This narrative review provides an overview of the problem and an update on strategies for the prevention, detection, and reduction/inactivation of bacterial contaminants in platelets. Bacterial contamination and septic transfusion reactions are major sources of morbidity and mortality. Between 1:1000 and 1:2500 platelet units are bacterially contaminated. The skin bacterial microflora is a primary source of contamination, and enteric contaminants are rare but may be clinically devastating, while platelet storage conditions can support bacterial growth. Donor selection, blood diversion, and hemovigilance are effective but have limitations. Biofilm-producing species can adhere to biological and non-biological surfaces and evade detection. Primary bacterial culture testing of apheresis platelets is in routine use in the US. Pathogen reduction/inactivation technologies compatible with platelets use ultraviolet light-based mechanisms to target nucleic acids of contaminating bacteria and other pathogens. These methods have demonstrated safety and efficacy and represent a proactive approach for inactivating contaminants before transfusion to prevent transfusion-transmitted infections. One system, which combines ultraviolet A and amotosalen for broad-spectrum pathogen inactivation, is approved in both the US and Europe. Current US Food and Drug Administration recommendations advocate enhanced bacterial testing or pathogen reduction/inactivation strategies (or both) to further improve platelet safety. Risks of bacterial contamination of platelets and transfusion-transmitted infections have been significantly mitigated, but not eliminated, by improvements in prevention and detection strategies. Regulatory-approved technologies for pathogen reduction/inactivation have further enhanced the safety of platelet transfusions. Ongoing development of these technologies holds great promise.

Fondaparinux in a critically Ill patient with heparin-induced thrombocytopenia: A case report

RATIONALE

Fondaparinux, as a factor Xa-inhibitor, is used off label to manage heparin-induced thrombocytopenia (HIT), but little experience with HIT patients has been reported in the literature. Moreover, the use of fondaparinux for full anticoagulation in critically ill patients with HIT and renal insufficiency is limited.

PATIENT CONCERNS

A trauma patient, who had received low molecular weight heparin (LMWH) and heparin to treat venous thromboembolism, developed thrombocytopenia and multiple organ dysfunction in the intensive care unit (ICU). Also, her deep venous thromboembolism (DVT) continued to progress.

DIAGNOSIS

The final diagnosis was HIT.

INTERVENTIONS

Fondaparinux was temporarily used for anticoagulation treatment of DVT for 7 days when another anticoagulant (argatroban) was unavailable. Although the patient had kidney dysfunction, a full therapeutic dose of 7.5 mg fondaparinux was administered every morning through subcutaneous injection for consecutive 7 days.

OUTCOMES

The patient's thrombocytopenia and thrombosis were successfully treated without bleeding complications during therapeutic fondaparinux administration.

LESSONS

This is the first case reporting the successful use of fondaparinux for full anticoagulation for DVT in a critically ill patient with HIT and renal insufficiency. Our experience suggests that fondaparinux might be an alternative for anticoagulation treatment in patients with HIT and kidney dysfunction if another anticoagulant (argatroban) is unavailable.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration

There is a growing appreciation for the contribution of platelets to immunity; however, our knowledge mostly relies on platelet functions associated with vascular injury and the prevention of bleeding. Circulating immune complexes (ICs) contribute to both chronic and acute inflammation in a multitude of clinical conditions. Herein, we scrutinized platelet responses to systemic ICs in the absence of tissue and endothelial wall injury. Platelet activation by circulating ICs through a mechanism requiring expression of platelet Fcγ receptor IIA resulted in the induction of systemic shock. IC-driven shock was dependent on release of serotonin from platelet-dense granules secondary to platelet outside-in signaling by αIIbβ3 and its ligand fibrinogen. While activated platelets sequestered in the lungs and leaky vasculature of the blood-brain barrier, platelets also sequestered in the absence of shock in mice lacking peripheral serotonin. Unexpectedly, platelets returned to the blood circulation with emptied granules and were thereby ineffective at promoting subsequent systemic shock, although they still underwent sequestration. We propose that in response to circulating ICs, platelets are a crucial mediator of the inflammatory response highly relevant to sepsis, viremia, and anaphylaxis. In addition, platelets recirculate after degranulation and sequestration, demonstrating that in adaptive immunity implicating antibody responses, activated platelets are longer lived than anticipated and may explain platelet count fluctuations in IC-driven diseases.

Assessing thrombocytopenia in the intensive care unit: the past, present, and future

Thrombocytopenia is common among patients admitted to the intensive care unit (ICU). Multiple pathophysiological mechanisms may contribute, including thrombin-mediated platelet activation, dilution, hemophagocytosis, extracellular histones, ADAMTS13 deficiency, and complement activation. From the clinical perspective, the development of thrombocytopenia in the ICU usually indicates serious organ system derangement and physiologic decompensation rather than a primary hematologic disorder. Thrombocytopenia is associated with bleeding, transfusion, and adverse clinical outcomes including death, though few deaths are directly attributable to bleeding. The assessment of thrombocytopenia begins by looking back to the patient's medical history and presenting illness. This past information, combined with careful observation of the platelet trajectory in the context of the patient's clinical course, offers clues to the diagnosis and prognosis. Management is primarily directed at the underlying disorder and transfusion of platelets to prevent or treat clinical bleeding. Optimal platelet transfusion strategies are not defined, and a conservative approach is recommended.

Blood platelets and sepsis pathophysiology: A new therapeutic prospect in critically [corrected] ill patients?

Beyond haemostasis, platelets have emerged as versatile effectors of the immune response. The contribution of platelets in inflammation, tissue integrity and defence against infections has considerably widened the spectrum of their role in health and disease. Here, we propose a narrative review that first describes these new platelet attributes. We then examine their relevance to microcirculatory alterations in multi-organ dysfunction, a major sepsis complication. Rapid progresses that are made on the knowledge of novel platelet functions should improve the understanding of thrombocytopenia, a common condition and a predictor of adverse outcome in sepsis, and may provide potential avenues for management and therapy.

Implementation of a rapid HIT immunoassay at a university hospital - Retrospective analysis of HIT laboratory orders in patients with thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a rare cause of thrombocytopenia and a potentially life-threatening adverse drug reaction. Clinical overdiagnosis of HIT results in costly laboratory tests and anticoagulation. Criteria and algorithms for diagnosis are established, but their translation into clinical practice is still challenging.

STUDY DESIGN AND METHODS

In a retrospective approach we studied all HIT related laboratory test requests within four years and evaluated data before (1st period, 24month) and after (2nd period, 24month) replacing particle gel immunoassay (PaGIA) and enzyme-linked immunosorbent assay (ELISA) by a chemiluminescent immunoassay (CLIA). HIT was confirmed by heparin-induced platelet activation (HIPA) test. Clinical pretest probability for HIT using an implemented simplified 4Ts score and platelet count were evaluated. Costs for laboratory tests and alternative anticoagulation were calculated.

RESULTS

In 1850 patients with suspected HIT, 2327 laboratory orders were performed. In 87.2% of these orders an intermediate/high simplified 4Ts score was found. Thrombocytopenia was present in 87.1%. After replacing PaGIA and ELISA by CLIA the number of immunological and functional laboratory tests was reduced by 38.2%. The number of positive HIT immunoassays declined from 22.6% to 6.0%, while the number of positive HIPA tests among positive immunological tests increased by 19%. Altogether, acute HIT was confirmed in 59 patients. A decline in the use of alternative anticoagulants was observed in the 2nd period.

CONCLUSION

Our study shows that in a university hospital setting HIT is well-known, but diagnosis requires a precise laboratory confirmation. Replacing PaGIA and ELISA by CLIA did not influence laboratory order behavior but results in reduced overall costs for laboratory diagnostics and alternative anticoagulation.

Recognition and Management of Hemostatic Disorders in Critically Ill Patients Needing to Undergo an Invasive Procedure

Abnormal laboratory coagulation test results are frequently documented in critically ill patients, and these patients often also need to undergo invasive procedures. Clinicians have an understandable desire to minimize any perceived heightened risk of bleeding complications in those patients who require invasive procedures. In this setting, prophylactic administration of platelets or plasma is commonplace. This review explores the nature of these sequential statements and the degree to which these statements are supported by evidence. We discuss the complexity of managing the low risk of procedure-related bleeding in a setting where coagulation tests fail to reliably predict this risk. The role of prophylactic transfusion of platelets and plasma and correction of medication-induced coagulopathy is also reviewed. New strategies are required to improve the evidence base, including novel methodological approaches or the use of a clinical scoring system.